More FC content? More niche rules and moves that allow you to enjoyably engage with mechanical crunch to your preferred degree?? More opurtunities for youthful hijinks and corresponding drama??? More PLANES????
Pros: there's bees that have pulsejets for butts called Rumblebees and there's also some Truly Wild narwhal squids.
Cons: I have read the whole book and desperately want to implement it, and my group has yet to have session 1 of vanilla Flying Circus.